MR-PheWAS for the causal effects of serum magnesium on multiple disease outcomes in Caucasian descent

Genome-wide association study meta-analysis supports association between MUC1 and ectopic pregnancy

STUDY QUESTION

Can we identify genetic variants associated with ectopic pregnancy by undertaking the first genome-wide association study (GWAS) leveraging two large-scale biobank initiatives?

SUMMARY ANSWER

We identified two novel genome-wide significant associations with ectopic pregnancy, highlighting MUC1 (mucin 1) as the most plausible affected gene.

WHAT IS KNOWN ALREADY

Ectopic pregnancy is an important cause of maternal morbidity and mortality worldwide. Despite being a common early pregnancy complication, the genetic predisposition to this condition remains understudied and no large scale genetic studies have been performed so far.

STUDY DESIGN, SIZE, DURATION

A GWAS meta-analysis including 7070 women with ectopic pregnancy and 248 810 controls from Estonian Biobank and the FinnGen study.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We identified ectopic pregnancy cases from national registers by ICD (International Classification of Disease) codes (ICD-10 O00), and all remaining women were considered controls. We carried out standard GWAS meta-analysis and additionally annotated GWAS signals, analysed co-localization with quantitative trait loci, estimated genetic correlations and identified associated phenotypes to characterize the genetic signals, as well as to analyse the genetic and phenotypic relationships with the condition.

MAIN RESULTS AND THE ROLE OF CHANCE

We identified two genome-wide significant loci on chromosomes 1 (rs4971091, P = 5.32×10-9) and 10 (rs11598956, P = 2.41×10-8) potentially associated with ectopic pregnancy. Follow-up analyses propose MUC1, which codes for an epithelial glycoprotein with an important role in barrier function, as the most likely candidate gene for the association on chromosome 1. We also characterize the phenotypic and genetic correlations with other phenotypes, identifying a genetic correlation with smoking and diseases of the (genito)urinary and gastrointestinal system, and phenotypic correlations with various reproductive health diagnoses, reflecting the previously known epidemiological associations.

LARGE SCALE DATA

The GWAS meta-analysis summary statistics are available from the GWAS Catalogue (GCST90272883).

LIMITATIONS, REASONS FOR CAUTION

The main limitation is that the findings are based on European-based ancestry populations, with limited data on other populations, and we only captured maternal genomes. Additionally, further larger meta-analysis or independent studies are needed to validate these findings.

WIDER IMPLICATIONS OF THE FINDINGS

This study encourages the use of large-scale genetic datasets to unravel genetic factors linked to ectopic pregnancy, which is difficult to study in experimental settings. Increased sample size might bring additional genetic factors associating with ectopic pregnancy and inform its heritability. Altogether, our results provide more insight into the biology of ectopic pregnancy and, accordingly, the biological processes governing embryo implantation.

STUDY FUNDING/COMPETING INTEREST(S)

N.P.G. was supported by MATER Marie Sklodowska-Curie which received funding from the European Union's Horizon 2020 research and innovation program under grant agreement No. 813707. This study was funded by European Union through the European Regional Development Fund Project No. 2014-2020.4.01.15-0012 GENTRANSMED. Computations were performed in the High-Performance Computing Center of University of Tartu. The authors declare no competing interests.

An Overview of Methods and Exemplars of the Use of Mendelian Randomisation in Nutritional Research

Objectives: It is crucial to elucidate the causal relevance of nutritional exposures (such as dietary patterns, food intake, macronutrients intake, circulating micronutrients), or biomarkers in non-communicable diseases (NCDs) in order to find effective strategies for NCD prevention. Classical observational studies have found evidence of associations between nutritional exposures and NCD development, but such studies are prone to confounding and other biases. This has direct relevance for translation research, as using unreliable evidence can lead to the failure of trials of nutritional interventions. Facilitated by the availability of large-scale genetic data, Mendelian randomization studies are increasingly used to ascertain the causal relevance of nutritional exposures and biomarkers for many NCDs. Methods: A narrative overview was conducted in order to demonstrate and describe the utility of Mendelian randomization studies, for individuals with little prior knowledge engaged in nutritional epidemiological research. Results: We provide an overview, rationale and basic description of the methods, as well as strengths and limitations of Mendelian randomization studies. We give selected examples from the contemporary nutritional literature where Mendelian randomization has provided useful evidence on the potential causal relevance of nutritional exposures. Conclusions: The selected exemplars demonstrate the importance of well-conducted Mendelian randomization studies as a robust tool to prioritize nutritional exposures for further investigation.

Causal Effect of Genetically Determined Blood Copper Concentrations on Multiple Diseases: A Mendelian Randomization and Phenome-Wide Association Study

Exposures to copper have become a health concern. We aim to explore the broad clinical effects of blood copper concentrations. A total of 376,346 Caucasian subjects were enrolled. We performed a Mendelian randomization and phenome-wide association study (MR-PheWAS) to evaluate the causal association between copper and a wide range of outcomes in UK Biobank, and we constructed a protein-protein interaction network. We found association between blood copper concentrations and five diseases in the overall population and nine diseases in male. MR analysis implicated a causal role of blood copper in five diseases (overall population), including prostate cancer (OR = 0.87, 95% CI 0.77-0.98), malignant and unknown neoplasms of the brain and nervous system (OR = 0.58, 95% CI 0.38-0.89), and hypertension (OR = 0.94, 95% CI 0.90-0.98), essential hypertension (OR = 0.94, 95% CI 0.90-0.98) and cancer of brain and nervous system (OR = 0.63, 95% CI 0.41-0.98). For male, except for dysphagia being newly associated with blood copper (OR = 1.39, 95% CI 1.18-1.63), other MR results were consistent with the overall population. In addition, the PPI network showed possible relationship between blood copper and four outcomes, namely brain cancer, prostate cancer, hypertension, and dysphagia. Blood copper may have causal association with prostate cancer, malignant and unknown neoplasms of the brain and nervous system, hypertension, and dysphagia. Considering that copper is modifiable, exploring whether regulation of copper levels can be used to optimize health outcomes might have public health importance.

Supplementary Information

The online version contains supplementary material available at 10.1007/s43657-022-00052-3.